A Handy Modafinil Dosage Field Guide

The Standard Modafinil Dosage

A standard modafinil (Provigil) dosage is 200 mg. Note that this differs from the standard armodafinil (Nuvigil) dosage of 150 mg. Less armodafinil is needed to produce the same effects because it's more potent and selective.

Modafinil tablets come in two flavors: 200 mg and 100 mg. The 200 mg variety is more frequently prescribed.

SWD: 200 mg once a day, taken approximately one hour prior to start of the work
shift.

Severe Hepatic Impairment: reduce dose to half the recommended dose.

Geriatric Patients: consider lower dose.

Exceptions And Precautions

In pharmacology, there’s heterogeneity when it comes to dose-response. What this means is that an effective dose for one person may be ineffective or unsafe for another person.

Consider the following guidelines.

Low-Dose Responders

Low-dose responders with anxiety may benefit from modafinil doses in the range of 50-100 mg but will find 200 mg overstimulating.

High-Dose Responders

High-dose responders with narcolepsy may need to take as much as 400 mg of modafinil in divided doses. For example, one study concluded "A split-dose 400-mg regimen may be superior to once-daily dosing for sustaining wakefulness throughout the entire waking day" [^1].

Modafinil Interactions Affect Dosage

Modafinil interacts with a number of drugs which can affect its metabolism and impact the appropriate dosage.

Modafinil Non-Responders

A fraction of population are modafinil non-responders. For genetic reasons they don't fully benefit from modafinil.

One hypothesis is that modafinil's efficacy in enhancing vigilance is contingent on catechol-O-methyl transferase (COMT) polymorphisms.[^3]

Individuals with the Val/Val genotype may realize greater improvements in their cognitive function. Conversely, people with the Met/Met allele experience neglibile enhancement.

Further reading:

“The combined effects on dopamine levels of amphetamine and high working memory load push individuals with the met/met genotype beyond the critical threshold at which compensation can be made,” suggest the researchers. They note evidence from other studies that too much dopamine activity in the prefrontal cortex may disorganize neural networks by activating inhibitory mechanisms.

Modafinil Drug-Drug Interactions

Modafinil is metabolized by the liver and excreted in urine. Less than 1/10th of the drug is excreted unchanged.

In patients with liver or kidney impairment, drug elimination can be slowed. Likewise, elimination in the elderly may be reduced on account of ordinary effects of aging. Modafinil dosages should be adjusted downward based on this information.